What groups can we form?

Perhaps I've been thinking of ensembles from the wrong direction, or communicating our options poorly. Whatever the case, it might be helpful to list some of the common ensembles. It's fairly easy to get music for these combinations.

String Quartet

2 violins, viola, cello

String Orchestra

Multiple players covering 2 violin, viola, cello and string bass parts

Brass Quartet

2 trumpets, 2 trombones (one of which must have a trigger in many cases)

Brass Quintet

2 trumpets, French horn, trombone, tuba or bass trombone

Woodwind Quintet

Flute, oboe, clarinet, French horn, bassoon

What other types of ensemble exist? For what other groups could you say "It's easy to get music for that combination of instruments?"